CD79-ALPHA CD79-BETA HETERODIMERS ARE EXPRESSED ON PRO-B CELL-SURFACES WITHOUT ASSOCIATED MU-HEAVY-CHAIN/

During B cell development, the surface expression of CD79 alpha/CD79 b eta heterodimers had been thought to begin in the pre-B cell stage whe re the heterodimers constitute pre-B cell receptors together with mu h eavy and surrogate light chains, Thereafter, in mature B cells, CD79 a lpha/CD79 beta associates with surface Ig to form B cell antigen recep tors, In this study, we revealed by using newly established mAb that C D79 beta was expressed on the surface of pro-B cells which had not und ergone the productive Ig gene rearrangement, Biochemical analysis show ed that CD79 beta on pro-B cells existed either as monomers or as disu lfide-linked heterodimers with CD79 alpha, noncovalently associated wi th four unidentified membrane molecules. Our finding that CD79 beta is expressed on earlier B-lineage cells than previously expected coincid es with the recent study in which CD79 beta-deficient mice exhibit a b lockade of B cell differentiation at the pro-B cell stage, Thus, it is speculated that the CD79 beta-containing complexes on pro-B cell surf aces may function to induce early B cell differentiation.